The sinoatrial node is an intrinsic pacemaker of the heart that generates electrical signals that can propagate through a cardiac electrical conduction system to various regions of the heart, such as to initiate contraction of cardiac muscle tissues. Some subjects experience conduction defects in the native electrical conduction systems of the heart. Such defects can manifest as uncoordinated or irregular cardiac function of one or more chambers of the heart. For example, in a subject with left bundle branch block (LBBB), electrical pulses may not be conducted normally along left bundle branches of the heart. This can result in a delayed activation of a left ventricle, such as with respect to a right ventricle. Thus, an LBBB can cause dyssynchrony between the left and right ventricles of the heart.
In various examples, cardiac rhythm management (CRM) systems can be used to treat cardiac dysfunction, such as to treat bundle branch block. Some CRM systems can include an implantable medical device configured to deliver electrical stimulation signals to one or more ventricles of the heart to facilitate resynchronization of the ventricles or otherwise improve cardiac function. For example, Pei et al., in U.S. Patent Publication No. 2011/0178567, entitled “TECHNIQUES FOR PROMOTING BIVENTRICULAR SYNCHRONY AND STIMULATION DEVICE EFFICIENCY USING INTENTIONAL FUSION,” refers to a method for pacing a ventricle having slowed atrioventricular conduction. Van Gelder et al., in U.S. Pat. No. 7,254,442, entitled “APPARATUS AND METHOD FOR “LEPARS” INTERVAL-BASED FUSION PACING,” refers to a method of LV-only fusion pacing therapy for a non-synchronous pair of ventricles.